Various machines have been developed for comminuting materials. Examples, with common names, include: shredders, having a relatively slow speed comminuting apparatus typically used for ripping and breaking hard, tough materials apart into relative coarse particles; chippers having a relatively high speed comminuting apparatus (either a rotating disc or a rotating drum) with sharp material reducing components typically used for cutting wood materials into small chips; and grinders having a relatively high speed comminuting apparatus (e.g., a rotating drum typically with robust and blunt material reducing components) that is located adjacent a sizing screen that is used to tear and shatter materials into a variety of particle sizes.
Grinders typically include reducing hammers on which replaceable grinding cutters (i.e., grinding tips or grinding elements) are mounted. Grinding cutters generally have relatively blunt ends suitable for reducing material through blunt force impactions. Screens are often used to control the size of the reduced material output from grinders. In contrast to the grinding cutters used on grinders, chippers typically include relatively sharp chipping knives configured to reduce material through a cutting/slicing action as opposed to a grinding action.